But the online retailer, which only offers the AmazonFresh service in the Seattle area, is coming back today with the release of its very own iPhone app.

Created by digital agency Metia/Seattle, the app allows shoppers to browse hundreds of products from the virtual aisles, schedule a delivery and even price compare with a new bar-code scanning feature.

GeekWire chatted with Metia/Seattle’s Andrew Martin to get an inside look.

What’s new in the app? “The AmazonFresh iPhone app extends the mobile grocery shopping experience to a native iPhone app. The application takes full advantage of the look, feel, and advanced functionality of the iPhone. There are some great new features including the ability to manage all your upcoming orders on the move and search products by scanning a barcode.”

What are your favorite features? “We love how fast the app is. Images load quickly, and purchases can be made with just a few taps. The barcode scanning is one of my favorite features, and I’m sure it will be a hit with AmazonFresh customers. It’s a great example of what can be done with a mobile app that can’t be done with a computer.”

Metia/Seattle's Andrew Martin

Did Metia/Seattle also build the Windows Phone 7 app? “We did. AmazonFresh took the bold step of building their app for Windows Phone first. We are excited that the full spectrum of Seattle’s smart phone users has access to AmazonFresh when they are on the go – we were flattered that AmazonFresh was so pleased with the Windows Phone app that they approached us again for the iPhone app. AmazonFresh customers love the Windows Phone app with recent comments in the marketplace including “Perfect App”, “Awesome” and “Impressively done.” We look forward to seeing what iPhone users think.”

What are the differences between the apps on the two operating systems? “There are differences in the user experience because each application was built for a different platform. The Windows Phone version of the application follows the Metro design approach, while the iPhone app is an excellent expression of the iOS experience. They both deliver the user experience that their respective users would expect and enjoy on their chosen phone. Things are a little different with mobile apps than they are on the web – customers get used to how apps work on their OS, so mobile application designers and developers need to produce apps that are intuitive and deliver the best customer experience specific to that platform.”

What were the challenges of building this iPhone app for the mobile shopper? “Buying groceries online is a unique shopping experience. The applications need to be easy to search, offering fast and accurate results. We knew that the app needed to be optimized to be fast and responsive for every search and interaction. Further, because the AmazonFresh application will be used by customers again and again, we needed to make sure that the simple tasks were super easy to do. Designing simplicity is often one of the hardest things to do. We expect that shoppers will use their AmazonFresh mobile applications throughout the week as they add-to and update their shopping lists, so it needs to offer a delightful user experience every time.